Fault indicating apparatus



March 16, 1954 BI G. WELBY 2,672,601

FAULT INDICATING APPARATUS Filed Feb. 27. 1952 2 Sheets-Sheet l Y 80/ 2 5 7 d6 5/ as as tgly xfl'assz' T] a 40 45 "I L5 .52 5 H.T.

27 INVENTOR BRIAN GUY WELBY March 16, 1954 B. G. WELBY 2,672,601

FAULT INDICATING APPARATUS Filed Feb. 27, 1952 2 Sheets-Sheet 2 INVENTOR BRIAN GUY WELBY @MMM ATTO RN EYS Patented Mar. 16, 1954 INDICATINGI. APPARATUS B ian Gus Welhy Sa hesh r Englan .55

ign-n; m, F xran sd l nwq m. E1 5 nd. aB iti hn mn y AppIicatiQnPFebI'Juany-JZ'I, 1952, S'erial'No. 273,761;

Claims amenity, nn ic tionfireat xitaim Eebrua 95iv 16;;Glaims.

This invention; relates generallyto f ault indieating apparatus or testingsystems for-the purpose-0t indicating thepositionof a movab1emember or the failure of a movable member to reach a prescribed: position, and more particularly to such apparatus or systems for'indicating whether a movable; member-is in a first; onsecqndposition to which itis; adapted to be moved by actuating means-response to a first: 013- second control-operation, or any-failure otiirstor-second actuating meanstoeffect the movement of a movable member'to; a first or-asecond position in response to a first or a second control operation respectively.

The invention is particgijarlyapplicable to tape perforators" or other kinds of teleprinter apparatus where each ofa group of-movable members in the formof mechanical" links is designated to be moved to a firstor-perfora-ting position on the energisa-tion by a first control operation or first actuating means in the form of an electromagnet individual to that linkand to a second; position on the energisation by asecond-control operation of second: actuatingmeans-in the form ofanother electromagnet; It isusuallyoi? importance with such apparatus that whenever'tne energisationof one of the eleetromagnetsfails: to produce the appropriatemovement ofthelink; the-iaultshoa-ld be indicated in some; way; for example a warning signal might be originated and/or the apparatns automatically stopped: working for; the fault to be cleared. v

The inventionalso has applicationtorelays of the kind in which a contact-operatingarmature is designed to be moved to one-position on the energisation of a relay-coil by a first-control operation and restored to-its originalposition by gravity or a spring when asthe result or a second control operation the energisati'onhas ceased: Again, it may be of importance to indic-atewhenever the energisation of the coil fails to producethe appropriate movement of the armature or whenever the armature fails-to restore afterwards;

Theinvention has of course other applications of'a character similarto those outlined in thepreceding paragraphs.

An object of the: present invention is to provide improved fault-indicatingapparatus for the purpose-stated.

A further object of the invention is-to provide 'a simple form of rapid fault finding or'testing system for a pluralityof movable members or a plurality of operations whiohis-respons-ive to the ocou-rrenceof a fault inanyaone; of said movable members or operations.

accordance with the present inventionapparatus for indicating the position of a member movable under the 'mfluenee or actuating m an p ise nsleett s cir t lud aaa m d el n r i in 1 3 1 9 31 i pedance s it mea d pendent n h i i .1 sa d: mo able. mambo; o! v r the Po n a i ir ten abe een tw .PQi t Qf'sa tim ede ca n indicating means responsive to the said variation f oten ia dificrsn a M re P ifiG -V; i?! @WQIQWE ith P E ent n ion mo tndicat n aaratus. ar. the De ens o ndicat n n t ilur f fi r se n q ia m ans' o f ect he mq em ntoia m ab m m e to a t t o a sesondi osi ioa a response. to a st r a SfidQ d: e mr np atien respectively, m r ses els rie l itc includiing'an impedance connected between v a first and a second point and-having an intermediate tapping switching means including amova-ble contact d bt io neag fi t 1 w l fired. q ntact connected-respectively, to tappings on said impecl n lo a e tw enlsai in e medi t boo ies id' rs in ndbatwsen sai ntermediate p n n sa dsewndipointa i kage ia causd. mov ble QQF QP FQ en a e sa qifirstfixssl n a 1 flidIS WIlSi fixaclgwnta t tQQQ iQiQg said'movable member is in saidfirst or said second position as the, case may be energising mcansjor causing each l" .QQ'P perati ns 1 .891 l? a p e al i erenaa tw E iF -LIQP a 13 Q tact nd a fir t. Pa nt '0 $?41L QI. ointas the case, may b endind a ng means respon i to the Ptefitia1 nce $53? QIHWPWQQQL v 3 31 movable contact and said' intermediate tapping should-saidmovahla con cti be n enga ment withsaid first fixed contact or said second rigged contact in rfifi onse to'said first operation or said second operation as the case may-be. I

Where either of said actuating means includes an electrical component arranged to beenergised response toithe appropriate one-of said control operations, said: energising=-means in. respect of this, control operation may comprise. electric-a1 on oc ionsioininasa dn :VablenGQntaWand-the appropr at command-n ts to s itahlepoints emissions c suiq t at component the-oa i who b r at ite uired a a l. ot he said. msm erstha t a tee; iro o dual t et and th ind ca n me ns may c ..isav e ec ni a ccn-itla mmon to a i t a sa t s ne air & e pons ve t tth fo r x: reli s f a. t poten ial: at iven, nt ny ne o sa d testing 9 rQ i ah e ti l ow e esc be by was at example as applied to alive-unit code tape per; forator of the teleprinter type, using double current operation. In such a'perforator eachcode group-of holes to be perforated is determined 'by the movement, i. e. the setting, to a first or perforating position (from the position occupied at the previous setting or from some intermediate or neutral position) of the appropriate ones of five movable members or mechanical links controlling the operation of the perforating pins, the movement of each link being effected by the energisation in response to a first control operation of first actuating means in the form of a first electromagnet individual to that link; at the same time each of the remaining links i. e. those pertaining to the perforating pins which are nonoperative for the particular signal being recorded, is moved to a second or non-perforating position by the energisation in response to a second control operation of second actuating means in the form of a second electromagnet individual to that link. After all the electromagnets appropriate to the required group of holes have been energised an additional electromagnet is energised to effect the actuation of the punch ing apparatus, for example to release a motor drive or to operate a punching solenoid, thereby causing the tape to be perforated in accordance with that group.

Such apparatus, however carefully designed, is liable to faulty operation of the setting electromagnets for the perforating pins, the energisation of a magnet in response to the appropriate control operation not being followed by the appropriate movement of the link individual to it when such a fault occurs during a setting operation-when any link required for the perforating operation does not move to its first position or when any of the non-perforating links does not move to its second position (to ensure its not making a perforation)=it is desirable to stop the apparatus or at least give some warning signal before the perforating operation is carried out. An example of a fault finding system according to the invention, and suitable for use in such an application, will now be described in more detail with reference to the accompany ing drawings, wherein:

Fig. 1 is a schematic circuit diagram of one embodiment of the invention;

Fig. 2 shows part of the diagram of Fig. 1 with the switches operated under fault conditions;

Fig. 3 is a schematic diagram of another embodiment of the invention;

Fig. 4 represents a schematic circuit diagram of a modification of Fig. 3; and

Fig. 5 is a schematic diagram of a fault indicator system, slightly modified with respect to that in Fig. 1 in combination with one form of tape perforator mechanism.

Referring now to Fig. 1, which illustrates schematically the principle of the fault indicating system the two field windings H! and H of a pair of electromagnets are connected in series between first and second points I2 and I3, the common point 14 of the two windings being earthed. Across points l2 and I3 is connected a resistor having an intermediate tapping l6, which for conveniences is near the center of the resistor though this is not essential. A single pole changeover switch I! has its movable contact [8 connected to common point I4, 1. e. to earth. One of the two fixed contacts IQ of the switch is connected to a tapping 26 on the resistor between tapping I5 and the first point 12; the other fixed contact 2| is connected to a tapping 22 on the resistor between tapping l6 and second point l3, these fixed contacts is and 2l 4 are therefore referred to as the first and the second fixed contacts respectively.

A link 23, which, in the case of a tape perforator testing system, may form part of the perforator pin selection mechanism, is associated with the field windings 10, ll of the electromagnets, for example it may form part of a common armature of both electromagnets, such that it is moved to a first position 24 or a second position 25 according to which of the field windings lil or H respectively is energised. The movable contact I 8 of the switch i1 is associated with the link 23 in such a manner that when the link is in its first position 24, the movable contact I8 engages the first fixed contact 19 and when the link is in its second position 25, the contact I8 engages the second fixed contact 2|. When the link is in an intermediate or neutral position (as illustrated by full lines in the figure) contact l8 engages neither of the fixed contacts l9 and 2!. The connection between the link 23 and the movable contact It may take various forms and is shown diagrammatically in the drawing as a parallel linkage 48. The link may however be designed to carry movable contact l3 itself, the mechanical coupling between the link and the contact being then a direct one.

Windings ill and H are energised by a suitable source, for example a battery 26 the positive pole of which is earthed and the negative pole connected to a movable contact 21 of another single pole changeover switch 28 the fixed contacts as and 38 of which are connected to first point 12 and second point 13 respectively. By causing contact 21 to engage contact 29 or 36, winding Iii or winding H is energised, as the case may be. These are the first and second control operations, respectively.

With the arrangement so far described, it will be seen that whenever the first control operation has been performed to energise winding H3, and movable contact IQ of switch IT is in engagement with contact [9, that part of resistor 15 which contains tapping I6 is unenergised and so this tapping is at earth potential. The only part of resistor 15 that is energised is that between tapping 26 and first point l2, this part of the resistor being included in a circuit in parallel with the energised winding IQ. The rest of the resister has the earth potential of common point M, to which it is connected by Way of second point 13 and winding H.

When however, while winding 10 is energised, movable contact I8 is in engagement with fixed contact 2|, as shown in Fig. 2, owing to the link 23 being in its second position 25, that part of resistor 15 which contains tapping i8 is energised, since it is now included in the circuit in parallel with the energised winding l6. Similarly if contact [8 is in engagement with neither of the fixed contacts is and 21 when winding H! is energised; the parallel circuit including tapping I6 is in this case completed by way of second point [3 and winding H. In either case tapping it has a negative potential, the said potential being more negative in the second case than in the first.

Similarly whenever the second control operation is performed so that winding H of the second electromagnet is energised; if movable contact I8 is in engagement with fixed contact 2!, tapping I6 is at earth potential; otherwise tapping l6 has a negative potential. A testing circuit as above described is individual to eac of a plurality of links such as 23.

Tapping is; connected-.- to that cathode. of a diode'valve 31:, The anodeiofi-thisvalnezisicon,- nected: to the anodesiof the-corresponding. diodes 3112c, 3.5:;associated; with: the testing. circuits of the otherlinks andrtotheanodeiof:a sixth diode 36; the cathoda ofwhich. is connected. to. a ter-. minal point; 3 1-. The potential of. this point: 3.1 is. normally. negajtiueibutxis raised to .earthpotem tial', for example by operation. of: normally open contact 45, when the. operation. ofthepunch motor,- or other powersource of the. perforaton, is: required: at: thevv end:- of eachlink-setting prQQ-w Thefianodesof; thediodesarealso c nn d to the. control grid: ofra triode valveefl; in the anode circuit: of: which is connected. the field w ding, .3 of the eIectmmag-net that: controls he motor or other. powersource (notshown). The. cathode of valve fia-isearthedand. the. con-. trol: rid is connectedto. the cathode byway of a resistor 40. v

In describing the operation, it; isfirstassumed that the apparatus isiunctioning correctly, that each link is in an intermediate position midway between its first and second positions: with movable contact 18 of eachswitch. ll similarly midway between the first and second fixed. contacts I 9' and 21, and that movable contact. 21, of each switch, 28, is midway. between fixed. contacts 29 and 3.0., The condition of eachlink and the as: sociated apparatus isthus. as. shown in Fig. 1. A all the windings are unenergised. a1l the..intermediate tappings. [6 are at earth potential. Terminal 3], and hence the cathode of diode 36', ar however at. a suificiently negative. potential to hold triode 38 cut off and so prevent the oper.-. ation of; the perforating mechanism.

Suppose now it, isdesired toperforate a. group of hole in accordance with the code, and it is assumed that the first. control operation, i. e. closing switch contact 2}! to contact29', represents; theperforating condition of the link 23, and the second, control operation, i. e;, the. re! verse closure of the contact 2,! represents the n r o o ditioner link 23;. The first. control operation-that is, operating. each mov able contact 2'! to fixed contact 29,.is according- 1y performed in respect of the links 23associatedwith thos holes, and accordingly each: win.d.-. ing; ID; of the corresponding; electromagnets; is energised: As the apparatus is funotioningcorrectly, each of those links is moved:to its first position 24, thereby; closing: the corresponding contactlt; to its fixed contact 19;, withtheresuit that the corresponding; intermediate; tap-r, pings It remain at earth potential;

It; will be appreciatedthat in. each: casethere: will bea brief interval between the time-when winding leis-energised and thetiniewhemthe link has-.moved sufiiciently to transfer contact l8 to contact !9 and that during this interval. tapping It has the negative potential; otherwise: associated with incorrect functioning of the apparatus. This transitory effect} camhowever be. ignored.

Simultaneously the second control. operations-t that is, operatingmovable-contact 2-.1; tonxed contact 3ilis performed inrespectof the non..- perforating links, and accordingly the. corresponding windings II are energised. As; again,-, the apparatus. is functioning; correctly,- each', of these links moves to itssecomi position-:Zithere: by operating the corresponding movable contact l8-. to; engage-fixed contact 21!, with the resultv h spondine: nterm di te contacts In emains taar-lh scien ist; her tansi ory-eflect: snninazpawr as. 'Th&naw1f5aE-Sflfllneditamne Suppose nowthat, the,apparatusisf mctioning n lrand" hatwh theze ntr pe ations- -re: p r r set thejlinkseq reo ear-t e perforati op r tion, i s; o more? tit-its;- st t n- T-hea l ondi io hus. rises-1. which movable; contact I' 8 eontrpll a y is not, in engagement with-,itstfixed. contact, 1-9 in response-to thefirst control; operation. 'Bhe corresponding intermediate tapping H5:- is; thus given a negative potential-, .which potentialrap plied as it is to. the. cathflt eotonootthefliodes 3| to 3 m nstriode: fit ut fi venr f er the'cathode of diode-3.6 hasbeenraised to,earth potential. The coil; taremains unenergized the punch mechanism thereiora does; not operate; and remains. unoperated until} the.; fault; is cleared.

. e u h: a sm. is. imi r y r vntes from operating. if onesof thelinks iails to rnove to t e no m ioratinapositionef er hee econd control operation has beenperiormedg,

To summarize: Eaehfsetting operation causes one of the electromagnets oi: each be energized-the: first-electromagnet lo; the case o a link. e u d. o h an rf 'ota meioneiiav tion,- the second, electromagnet- H 'iinthe case of each of the other linkernd leseeac moves to the appropriate-.1; position the-punch mechanism does not operate,

After each requiredgrouohas; meanperforated all five-links are automatically;-returnedgtojthe neutral position by resettingmechani'sm'i (not shown) prior to the. next; setting; operation; Alternatively, each link-mey-remainjn t first or second position, as the -case mambe untilqthe next setting operation; each link then IIIOVBStdi-r root from its previous-firstorsecond-nositiomto the new one, or-remains; whe 'itij sjift it: isrree. quiredto be inthe same posit as beforet. The neutral ition is thue nev rro. oise: by-vanll link 1 statically, except, of: "course in; error:

The existence. of a! ne ative potential? one any of the intermediate; tapi tin iszmay be: employed to operate some-alarm: device-,1 sucha-s warning lamp instead of or-inadditionto preventing-tine operating. of thepuncnmechanismr. A130,. coil 39' may be arranged, to operate; througln nor.- mally open contacts, 8th, a neon: tubenindicator r i on i ti f be-:31;andztseries-resistor fl supplied by the transformer: Q3;

Fig. 4 shows; a fault find n mr testingvsystem similar in principletocthatshown in-ili'ig. l, but slightly modified minor; respectz applied to. oneform of tape punching: mechanisxmof the teleprinter type.

In this, diagram whi'chgisipurelm schematic; only those parts of thextaipe,punchings-meche. anism are-shown which are: necessarysfor illuss, tratingwthe principle eithe-faultz-findingisystemt The; tape 5:4 passes: between an. anvili 55 and-z a die-plate; 56" and over a. guide. 511; and is: fed at each punching operation. by a.=. sprocket 585i and arm 60 of a three arm lever pivoted at 6|, the other arms of which constitute a punch hammer 62 and the armature 63 of a punch solenoid 64 respectively. The anvil block 55 is bored to receive a row of five punch pins 65 having restoring springs 66. The parallel link mechanism referred to above with reference to Fig. 1 comprises a link 61 and the limb 68 of a T-lever pivoted at 69, and the link 23 pivotally connected at its ends to both of these members. A central ferromagnetic portion of link 23 forms a common armature passing through the solenoid windings i and I I. The head It of each T-lever engages a pivot link H carrying a pivoted distance piece 12 slidable within a horizontal guide '13, so that according to the positions of the respective T- levers, as set through the links 23 by the code in use, the distance pieces 12 are either inserted between punch hammer 62 and the respective punch pins 65 or are withdrawn therefrom. The lower part '14 of each T-lever is arranged to actuate the switch i! which corresponds to that in Fig. l. The test circuit and the circuit connections are practically the same as in Fig. 1. The tube circuit is not reproduced in full, but the connections thereof are indicated by the leads numbered 50, 5|, 52 and 53 corresponding to those appearing in Fig. 1. Also the solenoid coils l0 and H are shown reversed in position as compared with Fig. 1. The switches I! and 28 are shown in the first of the control positions namely with contact 2! closed to contact 29, and contact l8 of switch I! closed to contact W. In this embodiment the power for the punch operation is supplied by the punch solenoid 54 from the battery through the additional switch contacts 16, which are closed by the relay coil 39 in the anode circuit of the triode 38 each time that a setting of the links 23 has been selected and has been found to be correct by testing as described above with reference to Fig. 1. Alternatively, in place of the punch solenoid 64 and the battery 75, motor operated mechanism may be employed for operating the punch, in which case the relay coil 39 and contacts i6 will be arranged to operate clutch engaging mechanism for the motor. f

In the above described embodiments each actuating means includes an electrical componentthe field winding of the electromagnet-arranged to be energized in response to the appropriate control operation, so that the energising means for causing each control operation to set up a potential difference between the movable contact and the first or second point as the case may be simply consists of the battery 26 and connections joining the movable contact and these points to suitable points in the energising circuits of these components. Where however a control operationthe second, saydoes not cause any electrical component to be energised, arrangements must be made so that as part of this control operation some source of supply, which may for convenience be that used for the first control operation, is applied between the movable contact and the second point. To illustrate this a further embodiment of the invention will now be described with reference to Fig. 3, in which those components already described in connection with the embodiment of Fig. 1 are given the same references, and those components that differ somewhat from but correspond to components already described are given the same references modified by the addition of the index I.

An electromagnetic relay includes a winding I which when energised displaces a contactoontrolling armature 23 against the force of spring 4| to a first position 24 indicated by the arrow; this spring restores the armature (thereby restoring the contacts controlled by it) to a second position as soon as winding I0 ceases to be energised. This second position of the armature is that illustrated in Fig. 3. The winding I0 is connected between first point l2 and point [4 of a test circuit similar to that already described. It is assumed that the relay includes among its switching units a single pole changeover switch ll; movable contact I 8 of this switch is shown in Fig. 3 as engaging second fixed contact 2| since the controlling armature 23 is shown in its second position. The arrangement is otherwise similar to that of Fig. 1 except that there is no winding or other electrical component connected directly between point l4 and second point (3, and that tapping It is connected to earth by way of a suitable electromagnetic indicating device t2for example having a flag 43 adapted to be released by an armature 44.

The first control operation consists as before in causing movable contact 2! of switch 28 to engage fixed contact 29, thereby energising winding N3 The second control operation, however, consists not in causing the energisation of some component connected directly between points it and I4 but in disengaging contact 2? from fixed contact 29 and causing it to engage for a short period the other fixed contact 30 before returning to the neutral position shown in Fig. 3.

The operation of the equipment is similar to that of the embodiment first described as far as the first operation is concerned. When it is desired to energise the relay, contact 27 is caused to engage contact 29. If the apparatus is functioning correctly, armature 23 moves to its first position 2& thereby changing over contact [8 of switch H to fixed contact l9. Consequently intermediate point 15, lying in the unenergised portion of resistor iii to the right of point 20, remains at earth potential and indicating device 42 does not operate. Should however the relay not be functioning correctly and the armature does not move sufficiently to cause contact Hi to engage fixed contact l9, intermediate tapping IB acquires a negative potential and the indicator 52 operates to give warning.

It will be seen that, as with the first described embodiment, there will be a short period between the energisation of winding I0 and the engagement of contact l8 with contact 19, during which tapping 6 has a negative potential. But, as before, this transition effect can be ignored. If indicator 42 tends to respond to such a brief excitation it may be fitted with a slug or other delay device to prevent this.

After the relay has functioned correctly and it is desired to cause it to restore, the second control operation is performed by changing over contact 21 of switch 28 to fixed contact 30. If then the relay restores sufficiently for contact Hi to change over to contact 2!, tapping IS remains in an unenergised part of resistor l5 to the left of point 22 and so retains its earth potential (apart from another possible transitory fall to a negative potential during the time taken for contact l8 to move from i9 to 2!). If on the other hand the relay does not restore sufiioiently for contact Hi to engage contact 21, tapping l5 lies in an energised part of the resistor and acaerator :to earth :from .etapping .22 is .acompleted by way of the rest .:of the. resistor, first point 12 and winding :l iii contact i8 is not engaging either :of the .fixed contacts; .or, if .acontact 1:8 1'has remained in engagement with contact 13, (for example owing to the armature sticking the operated position) the return to earth from tapping 22 :is completed by way of tapping 2 9 and contacts l9 and 1-8. in the iormer case of faulty operation the potential of it is more negative than in the latter .case due to the addi Itional voltage drop from point 44. In either case the indicator M operates.

It is desirable that moving contact .2 restores to neutral after each second --operation, for otherwise there would be wasteful Kenergisation of .a part of resistor l even though the relay had restored correctly. In this example the closure of contact 2! to contact 30 may be a test operation to determine whether the "link 23 has restored, as it should do, when contact is broken between 21 and 29.

The apparatus may also be used where neither actuating means includes an electrical component, and accordingly there are no windings or other components connected directly between points l2, l3 and 14. The movable member, whatever its form, is linked as before to the movable contact of the changeover switch and the apparatus acts in response to the control operations in a very similar manner to the action of the apparatus of Fig. 3 in response to the second control operation. Fig. 5 illustrates a fault finding or testing system operating in this manner. The circuit elements of the circuit system here illustrated corresponds to those in Figs. 1 and 2exceptthat-the coils l0 and H are omitted and the link 23 is adapted to be shifted from the position 24 to 25 and vice versa by mechanica'l or other means not shown in the drawing, and is linked to the movable contact 18 of switch I? and the movable contact 210T switch 2-8. The contacts 18 and 2-1 are shown in the same positions as in Fig. 3, and 'the leads 52 and 53 are assumed to be connected to the tube circuit as shown in'Fig. 1. In operation, the contact 21 ofswitchlt is moved to its first position i. e. fixed contact 29 at the same time as link 23 is moved to its first-position 24. If contact it engages fixed contact 19 the circuit is completed through that part of the resistor lying between the point I 2 and the tapping so that the point [6 is-at earthpotential. If, dueto faulty operation contact is does not close to contact It, but makes contact with the fixed contact 2?, or remains between the two end positions, a circuit is made through that part of the resistor containing the tapping l6, which thereby acquires a negative potential, which ap pears at the cathode of the respective diode of the respective test circuit and thereby gives a warning signal and prevents operation of the triode 38. Similarly, if either switch 23 or switch ll fails to operate.irrztheiidesire'd manner the tube circuit is rendered inoperative and the warning signal is given.

The above described embodiments arefor .illustrat-ive purposes-only-and admit of wide variations within thescope of the invention. In particular the details of the circuitry may be considerably modified-for example "other. compohetween the first and second'pfiintsaandthe nentsmaybe included-in series with the resistor 10 if desired. Whereit is desiredto pperate theap- 'paratu-s by A. 0. rather than D. suitable impedances maybe substituted for the resistor *connected between the first-andsecondpoints.

I claim:

l. Fault indicating apparatus for indicating -any failure of a movable member to reach a prescribed position in response to a control-operation, comprising an electrical test circuit "including an impedance connected between =l'irst and second points of said circuit, an energising "source for said impedance, two tapping points on said "impedance, switching means actuated by saidmovable member to close a circuit through one of said tapping points when the movable member is tin the prescribed control position and thereby to establish :a nc-fault potential difference between said tapping points, and to close a'circuit through another pointnf said impedance thereby establishing a fault potential difference between said first mentioned tapping points when the movable member is in any other position.

.2. Fault indicating apparatus for indicating any 'failure of a movable member to reach-aproscribed position in response to a control operation, comprising an electrical test circuit including an impedance connected between first and second points of said circuit, anenergising source for said impedance, two tapping points on said impedance, switching means responsive to the position assumed by said movable member having one contact making position in which an energising circuit for a portion of said impedance completed through one of said tapping points giving'riseto a no-fault-potentialdifferen'cebetween said tapping points upon completion of the control operation, whilst any other position of said switching means gives rise to a fault potential difierence between "said tapping points, and indicating means responsive to said potential difference.

3. Fault indicating apparatus for indicating any failure of a movable member to reach aprescribed'position in response to a-control operation, comprising an electrical test circuit including an impedance connected between first and said sec end points of said circuit, an energis'ing source for said impedance, two tappingpoints'on said impedance, switching means actuated by said movable member to complete an energizing circuit through 'difierent portions of said impedance, according to whether the switching means reaches or does not reach a contact-closing position-corresponding .to the prescribed position of the movable member, so as to'vary the potential diiference between said tapping points, and indicating apparatus responsive to said change of potential difference.

4. Fault indicating apparatus according to claim 3 wherein the :movable member is linked to said switching means having a :first .position corresponding to the prescribed position of the movable member-and causing the establishment of a first potential difference between the said points, and the said switching means hasat least oneother position corresponding to failure ofthe movable member to reach theprescri'bedposition, said other switch position causing the establishment of a second potentialdifference between the said points.

'5. Fault indicating apparatus according to claim 3, wherein theswitching means has :a first contact making position corresponding to a first potential at an intermediate point-of said impedance between isaid tapping points, -a' .-second contact making position corresponding to a different potential at said point and a further noncontact making position corresponding to a further potential at said point.

6. Fault indicating apparatus according to claim 3, including a, first switching means linked to the movable member and controlling the potential difference between said two tapping points of said impedance according to the position of the movable member, and a second switching means controlling the energisation of the impedance, said second switching means taking part in the control operation in response to which the movable member is actuated.

'7. Fault indicating apparatus according to claim 6, including actuating means for the movable member comprising an electromagnetic component connected in said test circuit said component being energised by the energising source for the impedance by operation of said second switching means.

8. Fault indicating apparatus according to claim 7, wherein the movable member has two positions corresponding to two closed positions of the first switching means and is adapted to be moved to the first position by energisation of said electromagnetic component and to be restored to the second position by mechanical means.

9. Fault indicating means according to claim 7, wherein the movable member has two positions corresponding to two closed positions of the first switching means and is adapted to be moved to said positions by electromagnetic components individual thereto and energized alternately by operation of said second switching means into two respective positions.

10. Fault indicating apparatus according to claim 3, for indicating any fault in the movement of a plurality of movable members comprising a plurality of test circuits, one for each movable member, an electrical potential responsive means connected to a tapping point of each impedance of the individual test circuits, and a further electrical potential responsive means common to all of said individual electrical potential responsive means such that the existence of a fault potential at any one of said tapping points retains said common electrical potential responsive means in one condition, whilst the absence of a fault potential at all tapping points causes the said potential responsive means to assume a second condition.

11. Fault indicating apparatus according to claim including a diode individual to each of said test circuits and connected to said tapping points, an electron tube circuit adapted to initiate a recording operation upon receipt of a given potential upon the grid of the tube and a common connection from each of said diodes to the grid of the electron tube.

12. Fault indicating apparatus according to claim 11 including a. further diode connected to said common connection and normally retained at a potential preventing operation of said electron tube circuit irrespective of the potentials at the tapping points, and means for applying a second potential to said further diode to allow operation of said electron tube circuit after all of said test circuit diodes have received potentials from their respective tapping points in conformity with a no-fault condition in each test circuit.

13. Fault indicating apparatus according to claim 3 for a tape perforator of the teleprinter type comprising a plurality of movable members each having a. test circuit, and a tape perforating member individual to each of said movable members and wherein each movable member is adapted to be set according to a code into a first or second position corresponding to the perforating or non-perforating condition of each of said tape perforating members, a common operating means for said tape perforating members, and control means for said common operating means responsive to the existence of a nofault condition in the impedance of all of said test circuits to initiate operation of the tape perforating members, and responsive to the existence of a fault condition in the impedance of any one of said test circuits to prevent operation of said tape perforating members.

14. Fault indicating apparatus according to claim 13, wherein the common control means comprises an electron tube circuit adapted to be energised to initiate the perforating operation upon receiving a given potential upon the grid thereof and a plurality of diodes, one for each test circuit connected between a common lead to said grid and a respective tapping on the impedance of their test circuits.

15. Fault-indicating apparatus for the purpose of indicating any failure of first or second actuating means to effect the movement of a movable member to a first or a second position in response to a first or a second control operation, as the case may be, comprising an electrical circuit including an impedance connected between a first and a second point and having an intermediate tapping, switching means including a movable contact adapted to engage first or second fixed contacts connected respectively to tappings on said impedance located between said intermediate tapping and said first point and between said intermediate tapping and said second point, a mechanical linkage for causing said movable contact to engage said first fixed contact or said second fixed contact according as said movable member is in said first or said second position as the case may be, energising means for causing each of said control operations to set up a potential difference between said movable contact and said first point or said second point as the case may be, and indicating means responsive to the potential difierence set up between said movable contact and said intermediate tapping should said movable contact not be in engagement with said first fixed contact or said second fixed contact in response to said first operation or said second operation as the case may be.

16. Apparatus as claimed in claim 15 including a second switching means performing the said first and second control operations consisting in applying energising potentials to said impedance between the movable contact of the first switching means and the said first and second points respectively, and wherein an electrical actuating means for said movable member is energised by the appropriate one of said control operations.

BRIAN GUY WELBY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 561,431 Pfatischer June 2, 18.96 687.9 18 Wood Dec. 3, 1901 1,784,504 Tanner Dec. 9, 1930 1,914,481 Brown June 20, 1933 2,293,708 Brown Aug. 25, 1942 2,369,678 1 McWhirter Feb. 20,1945 2,389,294 Ludi et al Nov. 20, 1945 

